The invention relates to the field of power electronics and power semiconductor modules.
Today power electronic equipment is commonly manufactured using field controlled power semiconductor devices like MOSFETs and IGBTs, either as discrete semiconductor devices or as power semiconductor modules, including several chips in parallel to achieve higher currents or including all the power semiconductor chips necessary for forming an inverter on an insulated substrate. Providing over-temperature protection of the power semiconductor components or providing temperature measurement capability is a requirement in most power semiconductor applications.
Typically, temperature sensors for temperature measurement or over-temperature detection are arranged on a base plate, a substrate or on a heat sink of a power semiconductor device or a power semiconductor module. Base plate, substrate and/or heat sink are thermally coupled to the semiconductor body where heat is dissipated. With the aid of loss models, an estimation is made about the thermal state of the semiconductor component, in particular about the junction temperature of the semiconductor chip(s) arranged within the power module or the device package.
In semiconductor devices or semiconductor modules which have a large spatial expansion, considerable deviations can be observed between the estimated temperature and the actual temperature of the semiconductor chip, in particular if the semiconductor chips are subjected to asymmetrical load and cooling conditions or to rapid changes of power dissipation. Furthermore, variations of the thermal resistances of a semiconductor component due to degradation caused by thermal cycling or power cycling are difficult to consider in the model used for temperature estimation.
The accuracy of the temperature measurement increases, the closer the temperature sensor is placed to the dissipating heat source, i.e. the pn-junction of a semiconductor component. For example, the temperature sensors can be glued to the semiconductor chip. However, the thermal coupling is a function of the thermal conductivity of the adhesive as well as of the dynamic characteristics of the temperature detection by the temperature sensor.
Finally, it is possible to integrate temperature sensors into the semiconductor chip of the semiconductor component in the form of resistors or diodes. In these cases it is necessary to provide additional circuit components either in the semiconductor body, which entails that valuable chip surface is lost for the integration of a temperature sensor.
As an outcome, the production process becomes more complex in response to the direct integration of thermo-sensors in the semiconductor chip by using additional elements and the yield can thus decrease. Altogether, measures for integrating additional components into the semiconductor chip increases costs. Finally, such integral solutions cannot be used for the temperature detection of standard semiconductor devices which do no include additionally integrated thermo-sensors.